1. Field of the Invention
The invention relates to the coating of partially masked substrates which coatings formed from combustible coating materials.
2. Description of the Prior Art
Various types of combustible coatings are applied to substrates to coat such surfaces. One class of such combustible coating materials is the paraxylylene-polymers which are formed from a vaporous diradical which is condensed to form the polymer. These polymers are commonly employed to coat or encapsulate various types of substrates. In some applications, it is necessary to mask defined areas on certain types of substrates in order to prevent the deposition of the coating on such defined areas during the coating operation. Such substrates which must be masked for this purpose include electrical circuit boards, hybrid circuits, and electrical components and modules. It may also be necessary to mask non-electrical substrates which require a masking/demasking operation in conjunction with the use of adhesives in an assemblying operation.
The exposed electrical contacts and connectors on the surface of circuit board substrates must be masked, for example, before the coating operation, and the masking must be removed by mechanical stripping before the coated substrate can then be put to its intended use. The cost incurred heretofore by the masking/demasking process can account, in many applications, for at least about 20 to 50 percent of the total cost of the coating.
Such costs have curtailed, to some extent, the use of these coating materials for various coating applications which could not stand such costs. A more simplified and effective masking process was sought, therefore, in order to expand the field of use of these coating materials.